The present invention relates to a method for applying an edge strip made of a viscous material to a surface which has at least one corner area, and more particularly, to a method for applying an adhesive bead to a vehicle window pane in which the material is discharged from a slot-shaped nozzle without interruptions also over the corner area and the nozzle being guided in a relative movement over the surface.
A known method, for example, applies an adhesive bead having a preferably triangular cross-section to a window pane along its edge. After the application of the adhesive bead, which may, for example, consist of an adhesive polyurethane material, the pane may then be glued into a pertaining vehicle body opening in either a mechanized or a manual manner. In such a conventional method, the adhesive bead is therefore applied without interruptions over the corner area of the surface to be provided with the edge strip as a result of the fact that the nozzle is guided along a circular arc of a small radius over this corner area as described in DE 37 30 344 A1. It was found, however, that in certain applications, the desired shape and/or uniformity of the adhesive bead can no longer be ensured if the curvature radius of the nozzle path becomes too small. With this known technique, it is therefore not possible to achieve an adhesive bead of a homogeneous cross-sectional shape and sharp edges.
The same is also true with regard to a known method for applying a spacer bead of a defined cross-section to a vehicle window pane disclosed in German Patent Document DE 43 26 179 A1. In order to apply the spacer bead with an angular course conforming to a respective corner area while maintaining the desired cross-section, it was suggested to apply the spacer bead sections adjoining the respective corner area so that they overlap in the corner area after which, by way of a press molding tool, which is provided particularly for this purpose, the thickened overlapping area is brought into the desired corner shape.
In DE 40 34 291 A1, a method is disclosed for applying a medium to a flat body via a robot in which a movement of the flat body by the robot and a rotating movement of the nozzle are coordinated with one another such that a moving sequence for the robot is obtained which is as simple as possible. There, for example, for applying an edge-side adhesive bead of a triangular cross-section to a vehicle window pane, the pane, during the application of the adhesive bead along one side of the pane, is subjected by the robot to a combined translational and rotational movement while simultaneously the nozzle is rotated such that the nozzle slot remains positioned transversely to the longitudinal direction of the adhesive bead strip to be applied.
In the method described in JP 1-184076 (A), an edge strip made of a viscous material is applied discontinuously in a surface corner area by a robot arm in that, when the corner is reached, the discharging of the material is stopped. The robot arm in a loop changes its moving direction parallel to the direction of the edge strip section to be applied next, and, when the corner is reached again, discharging of the material is continued.
In the method of JP 59-199079 (A), an edge-side adhesive bead is applied to the bottom side of a surface body by a nozzle which moves around the circumferential side of the surface body and leads out on the bottom side of the surface body.
DE 39 37 381 shows a device for the controlled application of linearly extending strands of pasty masses to a substrate in which case, simultaneously with the bead application, a visual degree-of-luminosity measurement is carried out at a point in advance of the application point and at a point following the application point. From a specific difference of the degree of luminosity of the two measuring points, a conclusion is drawn with respect to a sufficient thickness of the bead application, predominantly for a controlled application of a luminous solder paste to dull printed circuit boards. On the one hand, the known application control can be used only for pairings of a substrate and an application medium which, with respect to their luminosity, clearly differ from one another. For approximately equally luminous substrates or application media, or for beads of a defined shape and with a strongly dispersive reflex effect which are customary in the automobile industry, the known control cannot be used. Furthermore, this literature contains no suggestions as to how an adhesive bead can efficiently be applied in a manner corresponding to the shape along a track which bends in a sharp-edged fashion. An examination of the presence or absence of a bead application can, however, logically not provide information with respect to the production of a specific bead cross-section under difficult geometrical application conditions.
The present invention has an object of providing a method in which an interruption-free edge strip can be achieved at comparatively low expenditures with a course conforming to that of the surface edge also in a corner area of the surface edge.
This object has been achieved by a method in which (a) the material is discharged from a slot-shaped nozzle without interruptions also over the corner area, (b) the nozzle is guided in a relative movement over the surface, (c) when approaching a corner at the corner area the nozzle is rotated continuously from a position with a nozzle slot positioned essentially transversely with respect to a longitudinal direction (x) of a first applied edge strip section in the direction of a position with the nozzle slot positioned in parallel to a median line of the corner area and, during subsequent removal from the corner, continuously in the direction of a position with a nozzle slot positioned essentially transversely to a second longitudinal direction of a second applied edge strip section.
For applying the edge strip over a corner area, while the discharge of material is continued without interruption, the nozzle, when approaching the corner, is continuously rotated such that the nozzle outlet slot, which is normally situated transversely to the longitudinal direction of the edge strip to be applied, is continuously tilted such that it encloses an increasingly smaller acute angle with the median line of the corner area. When reaching the corner, the nozzle slot is preferably situated parallel to this median line. From the position reached in the corner, during the subsequent removal, the nozzle is continuously rotated further out of the corner, preferably until the nozzle slot is again situated transversely to the new longitudinal direction of the momentarily applied edge strip section.
Although, with the method of the present invention, the width of the applied edge strip is reduced toward one corner, this is not critical in most cases. As a result of saving process steps and a special tool for the shaping of the edge strip in corner areas, the method can be carried out in a very low-cost manner compared with the initially mentioned conventional methods while the quality of the edge strip is high.
An important use of the method of the present invention is the application of an adhesive bead of a triangular cross-section along the edge of a window pane. The new method allows the adhesive bead application in one operation possibly simultaneously with a spraying around of the sealing profile, in which case, while the triangular adhesive bead cross-section is maintained, a sharp-edged adhesive bead course which conforms with the pane edge can be achieved in the pane corner areas.
Because an important aspect is a relative movement between the nozzle and the surface provided with the edge strip, it is insignificant with respect to the sequence of movements whether only the nozzle, only the surface or both parts are caused to move.
A further advantageous aspect of the present invention involves applications in which the nozzle clearly has a lower weight than the body to which the edge strip is applied because then, for example, the robot-guided nozzle can follow the path of movements over a sharp-edged corner area much more steadily than the heavier body.
Preferred kinematics of the relative movement between the nozzle and the surface over a corner area are achieved in accordance with the present invention in that the nozzle is rotated about a point which is situated at the level of the exterior side of the edge strip to be applied. In a corner area with linear surface edges, the edge strip can then be applied over the corner area by this nozzle rotating movement combined with a translational movement along the surface edges. The direction of the transverse movement is changed from the direction parallel to one surface edge to the direction in parallel to the other surface edge as soon as the nozzle has reached the corner.